Method for removal of the current supply bolts from aluminum electrolysis furnaces



Aug. 4, 1959 G. BODEWEIN 2,897,585 METHOD FOR REMOVAL OF THE CURRENTSUPPLY BOLTS FROM ALUMINUM ELECTROLYSVIS FURNACES Filed June 6, 1955Inventor:

United States Patent IVIETHOD FOR REMOVAL OF THE CURRENT SUP- PLY BOLTSFROM ALUlViINUM ELECTROLYSIS FURNACES Gerhard Bodewein,Grevenbroich-Orken (Lower Rhine), Germany, assignor to VereinigteAluminium-Werke A.-G., Bonn, Germany, a corporation of Germany Theinvention relates to the anodes used in aluminum electrolysis furnaces.In the operation of these furnaces continuously operative anodes made ofpre-burnt artificial carbon blocks are used which must be continuouslyreplaced according to their consumption.

With this purpose in view lateral cylindrical or conic bolts generallymade of iron are employed, which enable the support of the anodes andthe supply of current to the same. The anodes are lowered into theelectrolyte in conformity with their consumption; they are submergedwith their lower part into the molten electrolyte having a temperatureof about 950 C.

The bolts are entered into the upper portion of the anode block andremoved from the same as soon as they reach the vicinity of the hotelectrolyte and the danger of their destruction arises.

The removal of these bolts from the anodes is difiicult since the latterin the moment of this removal are quite near to the electrolyte and areheated to approximately 700 C. Moreover, it must be kept in mind thatthese bolts are mostly held in a downwardly inclined direction towardsthe anode.

These bolts are for their removal pulled from the anodes by hydraulicmeans or by Withdrawal devices provided with screw threads; attemptshave been made to apply rotation to the bolts during their removal.

The devices are based upon the fact that the withdrawal devices for thebolts are supported upon the anode itself, the latter serving as anabutment; however, the known bolt removal methods and devices meet'withgreat difficulty mainly caused by the inclined position of the bolts andthe high operating temperature which exerts an enormous strain upon theservice personnel.

It is the main object of this invention to eliminate these difiicultiesand to facilitate the removal of the anode holding bolts from the anodesof the aluminum producing electrolysis furnaces.

It is also an object of the invention to facilitate the cooperation ofthe service personnel.

With these objects in view the invention will now be described morev indetail and with reference to the attached drawing showing a verticalsectional view of the 7 aluminum electrolysis furnace and its boltremoval device.

As apparent from the drawing, a current contact forming bolt 3 isentered into the anode 1, the latter reaching into the moltenelectrolyte 2. A hollow drill 4 is entered upon and surrounds thecontact bolt 3 to be removed from the anode 1. The drill 4 upon rotationserves to produce a cylindrical gap surrounding contact bolt 3. Thetubular drill 4 at its operative end preferably provided with hardcutters, not shown in the drawing; the drill is actuated by motor 5,which may be driven by compressed air or electricity. The device can beoperated without difficulty and the hollow drill 4 is automaticallycentered. Cooperation by the service personnel is restricted to theforward movement of the drill 4. The drill creates after a few minutesof revolution a bore having a width of 5 to 10 millimeters around thecontact bolt 3, which permits an easy removal thereof from the anode 1.

The device is for its manipulation provided with handles 6, and thetubular drill 4 with openings 7 for the removal of the powder created bythe rotation of the drill 4.

The application of the device is, as follows:

The hollow drill 4 is pushed over the protruding end of bolt 3 and setin rotation by the motor 5. The rotating tubular drill 4 is guided bythe contact bolt 3 and therefore needs only to be pressed forward toenter into the anode 1 until the depth of the contact bolt 3 is reachedand the latter is completely freed. The produced fines are removedthrough openings 7 of the tubular drill 4.

It will be apparent to those skilled in the art that the novelprinciples of the invention disclosed herein in connection with specificexemplification thereof will suggest various other modifications andapplication of the same. It is accordingly desired that in construingthe breadth of the appended claim they shall not be limited to thespecific exemplification of the invention described herein.

Having thus described the invention, what I claim as new and desire tobe secured by Letters Patent is as follows:

In a method for withdrawing a bolt having a portion embedded in apre-burned continuous anode of an aluminum electrolysis furnace with theaid of a hollow drill driven by an electric motor having arms, the stepscomprising selecting a hollow drill having an internal diam eterslightly larger than said bolt, whereby the drill may be telescoped overthe bolt and be guided and centered by the bolt, positioning said drillto surround said bolt and driving said drill with said motor, andmuscularly feeding said drill by axially directed pressure applied tosaid arms, whereby said drill will remove all of the materialsurrounding throughout the external periphery of said bolt therebyfreeing the bolt from its embedment, applying the muscular feed forcesand simultaneously a mo mentum compensating force to the arms in such arelationship that an average adult muscular force will be suflicient tocounteract the rotary momentum generated by the drilling and transmittedto the arms, and subsequently manually removing the bolt freed from itsembedment.

References Cited in the file of this patent UNITED STATES PATENTS

